Effect of Mass Fraction on Leaching Kinetics of Hydrophobic Ultraviolet Stabilizers in Low-Density Polyethylene

• Published in: Environmental science & technology 2023-12, Vol.57 (50), p.21428-21437
• Main Authors: Do, Anh T. Ngoc, Ha, Yeonjeong, Kwon, Jung-Hwan
• Format: Article
• Language: English
• Subjects: Additives; Aquatic environment; Boundary layers; Convection; Crystallization; Density; Diffusion; Diffusion coefficient; Diffusion layers; Diffusion rate; energy; Environmental conditions; environmental science; Fibers; geometry; Half-life; Hydrophobic and Hydrophilic Interactions; Hydrophobicity; Kinetics; Leaching; Low density polyethylenes; Occurrence, Fate, and Transport of Aquatic and Terrestrial Contaminants; Plastics; Polyethylene; Polyethylene - chemistry; technology; UV stabilizers; Water; Water Pollutants, Chemical - analysis
• ISSN: 0013-936X; 1520-5851; 1520-5851
• DOI: 10.1021/acs.est.3c06817

The leaching kinetics of five hydrophobic ultraviolet (UV) stabilizers from low-density polyethylene (LDPE) (micro)­fibers into water was evaluated in this study, with variation of the mass fraction (ω = 0.1–2.0 wt %) of the stabilizers. A one-dimensional convection–diffusion model for a cylindrical geometry, requiring partitioning between the LDPE fibers and water (K LDPEw) and the internal diffusion coefficients (D LDPE), was used to evaluate the leaching process and the leaching half-life of the target UV stabilizers at ω < 0.5 wt % (Case I). Diffusion through the aqueous boundary layer is the rate-determining step, and the leaching half-life is predicted to be very long (a few months to years) under unaffected conditions. When the UV stabilizers are supersaturated within LDPE fibers (i.e., ω > 0.5 wt %, Case II), the possible formation of a surficial crystal layer of the additives on the LDPE fiber extends the time scale for leaching compared to that in Case I due to the requirement of overcoming the crystallization energy. This study provides a fundamental understanding of the leaching profiles of plastic additives for assessing their potential chemical risks in aquatic environments; further studies under the relevant environmental conditions are required.